Manufacture of composites by a flexible injection process using a double or multiple cavity mold

ABSTRACT

The present invention generally relates to a mold assembly ( 32, 34 ) and a method of using the mold for the manufacture of composite parts which, more particularly, are generated from a strengthener in a generally solid phase and a matrix in a generally liquid phase. Various types of molds and processes may be used in order to impregnate a strengthener with a matrix such that a composite part may be manufactured, but the efficiency rate and the duration of the manufacturing process significantly varies depending on the chosen type of mold and process. The present invention relates to a mold assembly and to the manufacture of composites by using the mold assembly which includes the injection of the matrix in the mold assembly containing the strengthener and a deformable member ( 36 ) which favors the impregnation of the matrix toward the strengthener.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. Ser. No.12/958,594, filed Dec. 2, 2010, which is a divisional of U.S. Pat. No.7,866,969, issued to Ruiz et al., filed Apr. 17, 2006, both of which arein their entirety incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to the manufacture of compositeparts. More specifically, the present invention is concerned with themanufacture of a composite part by injection of a liquid phasethroughout a porous solid phase.

BACKGROUND OF THE INVENTION

Composite materials are generally considered engineering materials madefrom two or more components. One component is often a fiber or poroussolid phase, generally called the strengthener, which gives the materialits tensile strength, while another component is often a resin or liquidphase, generally called the matrix, which binds the strengthenertogether and renders the composite material generally either stiff andrigid or deformable as a whole.

Several processes used in the manufacture of composite parts consist ofimpregnating the strengthener with the matrix, which may be a polymer (aresin) or any material that is liquid at the injection temperature.Variants of this family of processes are now grouped, under the genericterm LCM or Liquid Composite Molding. Although they are used principallyfor the manufacture of polymer matrix composite parts, LCM processes arealso encountered in biomedical and electronics applications, for examplewhen injecting a polymer to insulate microelectronic circuits. A moltenmetal may be injected instead of a polymer resin in order to manufacturemetal matrix composite parts.

Polymer matrix composite manufacturing processes may be separated intoseveral categories:

Contact Molding Process

This manual method generally uses a half-mold on which the drystrengthener is set in layers that are impregnated by hand.

Autoclave Process

The composite part is generally manufactured by hand frompre-impregnated strengtheners and then cured in an autoclave. Thismethod is widely used in aeronautics, most notably in the militarysector. However, its cost remains generally high.

RTM (Resin Transfer Molding) Process

The matrix in its liquid state is generally injected throughout astrengthener confined in a rigid mold. Liquid injection in the RTMprocess may be carried out at ambient temperature or at a highertemperature by heating either the injected liquid, the mold or both.

VARTM (Vacuum Assisted Resin Transfer Molding) Process

A vacuum is generated inside the mold in order to facilitate andaccelerate matrix injection.

CRTM (Compression Resin Transfer Molding) Process

Also called injection-compression, the CRTM process generally consistsof opening slightly the gap between the mold halves during injection toaccelerate the liquid flow, after which the part is consolidated andsized to specification by lowering the press on the molds or one of themold halves on the other.

VARI (Vacuum Assisted Resin Infusion) Processes

The strengthener is generally arranged beneath a plastic film or elasticmembrane, creating a compartment which may be placed under vacuum. Theliquid then infuses into the strengthener by gravity.

RTM Light Process

This variant combines the advantages of deforming one boundary of themold, as in the VARI process, with an imposed injection pressure, as inthe RTM process. The mold consists of one or two thin metal or compositeshells, which may be deformed under the pressure of injection. A firstvacuum usually ensures closure of the mold, while a second vacuum isgenerated inside the cavity to accelerate injection.

Other Variants

Numerous other variants of the LCM processes exist, which may beassociated with one or another of the previously described maincategories. For example, the VEC injection process uses reservoirscontaining a non-compressible fluid to strengthen the walls of a moldthat are not in contact with the part. Preferential flow channels mayalso be created by various means in an outer layer of the strengthener(SCRIMP process), in one of the mold walls or inside the cavity, inorder to facilitate liquid infusion or injection.

The quality of parts manufactured by contact molding is generally loweron average than that of injected parts. Labor costs are considerable aswell, since each layer of the strengthener must be precisely positionedin the cavity and the laminate impregnated by hand. During impregnationby the liquid, air bubbles are often entrapped inside the compositepart. This constitutes the principal problem with contact molding andexplains notably the large variations observed in part weight. A seconddisadvantage stems from the difficulty of ensuring constant partthickness and uniform fiber content, two critical parameters that governthe quality and mechanical properties of the composite part. Finally,another problem arises from increasingly strict government regulationsconcerning toxic gases or vapors generated during open moldmanufacturing.

LCM processes based on the use of closed molds significantly eliminatemost gaseous emissions during manufacturing. Conventional liquidinjection molding is done using two rigid half-molds: the base generallydesignates the bottom portion of the mold, which remains immobile andthe punch designates the top portion, which is raised in order to openthe mold and free the part at the end of the manufacturing cycle.Between these two half-molds lies a cavity in which the strengthener isarranged and into which the injection occurs.

The RTM process and its variants VARTM and CRTM are generallyappropriate for the manufacture of structural composite parts, butconstant thickness remains difficult to achieve because of the nonuniform shrinkage of the resin during the cure. It is not always easy toeliminate porosity completely in injected parts, even by creating vacuumin the cavity before injection. Finally, the biggest difficulty isassociated with the injection time, which is generally too long forstrengtheners with high fiber content (i.e., more than 50%).

Overall, average surface appearance, low geometrical precision of theparts and limits regarding fiber content and injection time all reducethe range of applications of RTM process and its derived processes suchas heated RTM, VARTM and injection-compression (CRTM). One constraintpeculiar to CRTM process should also be mentioned. In general, the punchcloses along a vertical axis, which results in practically nocompression of the strengthener in the vertical zones of the cavity,while maximal pressure is exerted in the horizontal zones. This problem,in addition to difficulties inherent to the complexity of the processand risks of air entrapment during the compression phase, significantlylimit the applications of CRTM process. It should be noted thatcompression of one half-mold over the other may also be performed byzones, but this significantly complicates the manufacturing of the mold.

Recently, new vacuum impregnation processes (VARI) have been introduced,which present the advantage of not requiring a cover mold. In theseso-called liquid aspiration infusion processes, the strengthener isstill arranged in the mold cavities, but is then covered with animpermeable membrane sealed to the outer edges of the mold. The airinside the cavity formed between the membrane and the mold may then beevacuated using a vacuum pump. Atmospheric pressure then compacts thestrengthener, while the liquid flows from an external source into thestrengthener-filled cavity under vacuum. In this type of VARI process,liquid infusion into the strengthener is carried out under vacuum at lowflow rate under the single effect of static pressure due to gravity. Theinclusion of air bubbles is thus eliminated, solving one of the problemsencountered in other injection variants. However, the effect of gravitygenerally introduces non uniformity into the impregnation of thestrengthener for large parts. In spite of the apparent simplicity ofVARI processes, problems persist because the flow of the viscous matrix,such as for example resin, is difficult through strengtheners of lowpermeability. The fiber contents and dimensional accuracy of partsinfused by VARI process are generally lower than the levels that may beaccommodated by RTM process. Since resistance to resin penetrationincreases with the distance to be crossed, portions of certain parts mayremain dry while excesses of resin accumulate in other zones.

In order to resolve these problems, variants of these processes havebeen recently developed, which artificially increase localpermeabilities in the strengthener and thus decrease filling time. Theseinclude resin-dispersing permeable felts on one surface of thestrengthener, networks of tubes to distribute the liquid matrix flowthroughout the cavity, preferential flow channels or groovesincorporated into the surface of the mold and so on. All of thesemethods pose particular problems. The use of felt leads to increasedwaste of material, which is incompatible with mass production. Networksof tubes and flow channels generate practical development difficulties,which can be overcome only at the expense of generally costly trialperiods. Finally, infusion still remains excessively slow compared toinjection. The pressure gradient driving liquid penetration is muchgreater in an injection process than the infusion gradient which cannotexceed ambient atmospheric pressure minus the residual pressure insidethe cavity under vacuum.

OBJECTS OF THE INVENTION

An object of the present invention is therefore to provide a mold and amethod of using the mold which allows to rapidly and efficiently injectunder pressure the liquid matrix required to manufacture the compositepart, without having to wait for complete impregnation of thestrengthener.

A further object of the present invention is therefore to provide a moldand a method of using the mold which allows controlling the progressionof the matrix flow front through the strengthener to increase thecomposition, geometrical and mechanical quality of the composite partduring the various manufacturing steps.

Another further object of the present invention is to provide a mold anda method of using the mold which allows producing one or more than onecomposite part at the same time and with generally the same moldinjection equipment.

SUMMARY OF THE INVENTION

More specifically, in accordance with the present invention, there isprovided a mold assembly for generating a composite part from astrengthener in a generally solid phase and a matrix in a generallyliquid phase; the mold assembly including a base mold including astrengthener chamber for receiving the strengthener and a matrixinjection inlet for injecting the matrix in the strengthener chamber;the mold assembly further including a cover mold including a compressionchamber and a fluid control aperture for injecting a fluid in thecompression chamber; the cover mold being so configured as to besealingly mounted on the base mold whereby the strengthener chamber andthe compression chamber are adjacent; and the mold assembly furtherincluding a deformable member so provided in a gap defined by thestrengthener chamber and the compression chamber as to pressurize thematrix toward the strengthener upon compression by the fluid.

There is furthermore provided a mold assembly for generating apredetermined number of composite parts from strengtheners in agenerally solid phase and from matrix in a generally liquid phase; themold assembly including a base mold including a strengthener chamber anda cover mold including a compression chamber; the mold assembly furtherincluding at least one frame assembly, each including a separatordefining a further respective strengthener chamber and a furtherrespective compression chamber; the at least one frame assembly being soconfigured as to be sealingly stacked one next to the other and betweenthe base mold and the cover mold, whereby each of the strengthenerchamber faces one of the compression chamber to define adjacent pairs ofchambers; the mold assembly further including matrix injection inletsfor injecting the matrix in the strengthener chambers; the mold assemblyfurther including fluid control apertures for injecting a fluid in thecompression chambers; and the mold assembly further including deformablemembers so provided between the adjacent pairs of chambers as topressurize the matrix toward the strengthener upon compression by thefluid.

There is furthermore provided a mold assembly for generating apredetermined number of composite parts from strengtheners and matrix;the mold assembly including a base mold including a contact wall; themold assembly further including at least one frame assembly soconfigured as to be sealingly stacked one next to the other on the basemold defining a stacking chamber thereby; the mold assembly furtherincluding matrix injection inlets for injecting the matrix in thestrengtheners trough the base mold and the at least one frame assembly;the mold assembly further including deformable elements, each having arespective compression wall and a further respective contact wall, thedeformable elements being so configured as to be alternatively stackedwith the strengtheners in the stacking chamber whereby each of thecontact wall faces one of the compression wall; and the mold assemblyfurther including a cover mold including a further respectivecompression wall and being mounted in the stacking chamber.

There is furthermore provided a mold assembly for generating a compositepart from a strengthener and a matrix; the mold assembly including abase mold including a strengthener chamber for receiving thestrengthener and a matrix injection inlet for injecting the matrix inthe strengthener chamber; the mold assembly further including a covermold including a compression chamber and a fluid control aperture forinjecting a fluid in the compression chamber; the cover mold being soconfigured as to be sealingly mounted on the base mold whereby thestrengthener chamber and the compression chamber are adjacent; and themold assembly further including a deformable membrane provided in a gapdefined by the strengthener chamber and the compression chamber; wherebyupon operation, the matrix is injected via the injection inlet in thestrengthener located in the strengthener chamber, a first portion of thematrix impregnates the strengthener and a second portion of the matrixremains in the strengthener chamber and deforms the deformable membranethereby, the second portion being forced into the strengthener by thefluid pressurizing the deformable membrane when injected in thecompression chamber via the control aperture.

There is furthermore provided a method for generating a composite partfrom a strengthener and a matrix including sealingly positioning adeformable member in between a first chamber of a first mold portion anda second chamber of a second mold portion, the first chamber receivingthe strengthener; impregnating the strengthener with the matrix injectedin the first chamber; compacting the matrix toward the strengthener bypressurizing a controlling fluid injected in the second chamber on thedeformable member.

There is furthermore provided a method for generating a pre-determinednumber of composite parts from strengtheners and matrix includingsealingly positioning a deformable member in between a strengthenerchamber of a first mold portion and a compression chamber of a secondmold portion, the strengthener chamber including the strengthener;repeating the sealingly positioning a deformable member by stacking anumber of subsequent mold portions one next to the other determined by apredetermined number of parts to manufacture; impregnating thestrengtheners with matrix injected in the strengthener chambers;compacting the matrix toward the strengthener by pressurizing acontrolling fluid injected in the compression chamber on the deformablemember.

There is furthermore provided a method for generating a predeterminednumber of composite parts from strengtheners and matrix includingpositioning an alternating stack of strengtheners and deformable membersin a stacking chamber generated by sealingly mounting frame assemblieson a base mold assembly; impregnating the strengtheners with matrixinjected in the stacking chamber; compacting the matrix toward and alongthe strengtheners by pressurizing on the stack of strengtheners anddeformable members.

Other objects, advantages and features of the present invention willbecome more apparent upon reading of the following non-restrictivedescription of preferred embodiments thereof, given by way of exampleonly with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1 is a side section view of a mold according to a first embodimentof the present invention;

FIG. 2 is a perspective view of the base mold shown in FIG. 1;

FIG. 3 is a top view of the base mold shown in FIG. 2;

FIG. 4 is a side section view of the base mold shown in FIG. 2;

FIG. 5 is a side section view of the cover mold shown in FIG. 1;

FIG. 6 is a side section view of the mold of FIG. 1 provided with astrengthener;

FIG. 7 is a side section view of the base mold showing a first step in aprocess for manufacturing a composite part;

FIG. 8 is a side section view of the base mold showing a second step ina process for manufacturing a composite part;

FIG. 9 is a side section view of the mold showing a third step in aprocess for manufacturing a composite part;

FIG. 10 is a side section view of the mold showing a fourth step in aprocess for manufacturing a composite part;

FIG. 11 is a side section view of the mold showing a fifth step in aprocess for manufacturing a composite part;

FIG. 12 is a side section view of the mold showing a sixth step in aprocess for manufacturing a composite part;

FIG. 13 is a side section view of the mold showing a seventh step in aprocess for manufacturing a composite part;

FIG. 14 is a side section view of the mold showing an eight step in aprocess for manufacturing a composite part;

FIG. 15 is a side section view of the mold showing a ninth step in aprocess for manufacturing a composite part;

FIG. 16 is a side section view of the base mold showing a tenth step ina process for manufacturing a composite part;

FIG. 17 is a side section view of the base mold showing an eleventh stepin a process for manufacturing a composite part;

FIG. 18 is a side section view of the base mold, showing a twelfth stepin a process for manufacturing a composite part;

FIG. 19 is a side section view showing a mold according to a secondembodiment of the present invention;

FIG. 20 is a side section view showing a mold according to a thirdembodiment of the present invention;

FIG. 21 is a side section view showing a step of compression generatedby tubes of the mold of FIG. 20;

FIG. 22 is a partial isometric view showing a cover mold according to afourth embodiment of the present invention;

FIG. 23 is a top plan view showing the fluid passage network of thecover mold of FIG. 22;

FIG. 24 is a side section view showing an impregnation step in the moldaccording to the fourth embodiment of the invention;

FIG. 25 is a side section view showing a fluid injection step in themold of FIG. 24;

FIG. 26 is an exploded side section view showing a mold according to afifth embodiment of the present invention;

FIG. 27 is a side section view showing a fluid injection step in themold of FIG. 26;

FIG. 28 is a side section view showing a compression step in the mold ofFIG. 26;

FIG. 29 is a side section view showing a mold according to a sixthembodiment of the present invention;

FIG. 30 is a side section view showing an impregnation step in the moldof FIG. 29;

FIG. 31 is a side section view showing a compression step in the mold ofFIG. 29;

FIG. 32 is a side section view showing a cure step in the mold of FIG.29;

FIG. 33 is a side section view showing a membrane in the mold of FIG.29; and

FIG. 34 a mold according to a seventh embodiment of the presentinvention.

DETAILED DESCRIPTION

Generally stated, the present invention relates to the manufacture of acomposite material by injecting in a mold assembly a generally liquidphase, called the matrix, throughout a strengthener that is in agenerally solid phase with a method of injection that favors anefficient impregnation of the matrix in the strengthener. The matrix isgenerally a resin, such as for example a thermoset or a thermoplasticpolymer or a liquid metal, and the strengthener is a fibrous, granularor any other type of porous material. Examples of commonly usedthermoset polymers include epoxy, polyester, vinylester or phenolicresins, and examples of commonly used liquid metals include aluminum ormagnesium. The process of injection of the matrix into the strengtheneris often used for the manufacture of composite parts. For example, apolymer, a metallic or a ceramic matrix may be reinforced by glass,carbon, kevlar, metal, ceramic or other strengtheners. In the case offibrous strengtheners, cloths or mats made of glass fiber, carbon,kevlar, aramide, natural fibers are generally used. The range ofapplications for such composite parts manufactured by such a processcovers, amongst others, the field of transport vehicles (marine,automotive, aeronautical) and may also be used in the sport, biomedicaland electronics sectors.

The illustrative embodiment of FIG. 1 shows a mold assembly 30 used inthe injection of a matrix into the strengthener for the manufacture ofcomposite parts. The mold assembly 30 is generally rigid and includes abase mold 32, a cover mold 34 and a deformable member, show in theillustrative embodiment as a membrane 36.

The base mold 32 is illustrated in more details in FIGS. 2, 3 and 4 andincludes a strengthener chamber 38 which is defined by a contact wall 40and by peripheral walls 42. When in use, the strengthener chamber 38 isgenerally so configured as to receive a strengthener and to provide thespace into which the matrix is injected to manufacture the compositepart.

The base mold 32 and its strengthener chamber 38 are generally designedto the dimensions of the strengthener to be injected with the matrix. Itis easily understandable to the skilled reader that in the Figures, thebase mold 32 is presented with a configuration adapted to receive a flatrectangular strengthener plate, but can be configured to suit variousshapes of strengthener or a combined strengthener with a foamed core.

The base mold 32 further includes an evacuation outlet 44 and aninjection inlet 46. The evacuation outlet 44 extends from thestrengthener chamber 38 to the external surface of the base mold 32, andis so configured as to be connected to a vacuum source (not shown) togenerate suction or vacuum in the strengthener chamber 38. More than oneevacuation outlet 44 may be included in the base mold 32 and each ofthem may be connected to more than one vacuum source (not shown).

The injection inlet 46 extends through the base mold 32 with a first endbeing so configured as to be mounted to a matrix source (not shown) andwith a second end in communication with the strengthener chamber 38. Inthe illustrative embodiment, the second end includes a diffusion passage50 extending along any desired path in the strengthener chamber 38 tomaximize the diffusion of the matrix therein. Of course, more than oneinjection inlets 46 may be provided around the strengthener chamber 38or at its periphery.

The shoulder 47 of the base mold 32 includes grooves 48 which arerepresented, as an example, as having a generally triangularcross-section which helps to hold the membrane 36 and to sealingly mountthe cover mold 34 to the base mold 32. Optionally, additional standardmolding elements, such as for examples o-ring sealants, tubes, guides,or demolding devices (not shown) may be added to facilitate mold closureand mold opening.

Turning now to FIGS. 5 and 6, the cover mold 34 includes a compressionchamber 52 which is defined by a compression wall 54 and by peripheralwalls 56. When in use, the compression chamber 52 is so configured as toreceive a fluid or pressure means and has a geometry which is generallydetermined by the configuration of the part to be molded, as will befurther described hereinbelow.

The cover mold 34 further includes a fluid control aperture 58 and avent 60. The fluid control aperture 58 extends from the external surfaceof the cover mold 34 to the compression chamber 52, and is so configuredas to be connected to a pressurized fluid source (not shown) to providepressure in the compression chamber 52. More than one fluid controlaperture 58 may be included in the cover mold 34 and each of them may beconnected to more than one pressurized fluid source (not shown).

In the embodiment shown in FIG. 6, a single fluid control aperture 58 isextending in the cover mold 34 in a direction which is generally alongthe direction of the injection inlet 46 in the base mold 32.

The vent 60 also extends from the compression chamber 38 to the externalsurface of the cover mold 34, and is so configured as to expel the fluidcontained in the compression chamber 52. Alternatively, the vent 60 isconnected to a vacuum source (not shown) to selectively provide suctionor a partial vacuum in the compression chamber 52, or includes valves(not shown) to regulate the flow of fluid in the compression chamber 52.More than one vent 60 may be included in the cover mold 34.

The shoulder 61 of the cover mold 34 includes ridges 62 which are soconfigured as to cooperate with the grooves 48 of the base mold 32 andare represented, as an example, as having a generally triangularcross-section. The assembly of the ridges 62 and grooves 48 generallyextends around the shoulders 47, 61, in the periphery of the molds 32,34 to help hold or locate the membrane 36, to mount the base mold 32 andthe cover mold 34 together and to seal the chambers 38, 52.

In FIG. 6, the mold assembly 30 contains the strengthener 66 in thechamber 38 of the base mold 32. When mounted together, the cover mold 34and the base mold 32 delimit a gap 64 which includes the two chambers38, 52 separated by the membrane 36.

The gap 64 is shown in FIG. 6 as having a total thickness or height h,including the compression chamber 52 having a thickness or heighth.sub.f and the strengthener chamber 38 having a thickness or heighth.sub.s. The height h is adjusted as a function of the thickness of thestrengthener being injected with the matrix, in order to control thefilling of the strengthener by the matrix, as will be further explainedhereinbelow. Also the variations of the height h allow the manufactureof composite parts of variable thickness.

The membrane 36 is provided in a cavity or gap defined by thestrengthener chamber 38 and the compression chamber 52. The membrane 36is generally a thin impermeable layer such as a plastic film, an elasticmembrane, or a generally deformable foam not necessarily having auniform thickness, or any type of material impermeable to the matrixused. Alternatively, the membrane 36 may be permeable to gas only.

The membrane 36 is sufficiently flexible to be deformed under pressureinduced in the chambers 38, 52, such that the height h.sub.f and theheight h.sub.s are variable. As will be described hereinafter, this hasthe effect of facilitating the impregnation of the matrix in thestrengthener. The deformation of the membrane 36 is nevertheless limitedby the thickness h of the gap 64 which, as mentioned hereinabove, is notnecessarily uniform.

The surface finish of the contact wall 40 depends on the desired surfaceappearance for the composite part to manufacture. Usually, the base mold32 is made of metal, ‘but it can also be’ made of any material normallyused to manufacture injection molds, for example, an epoxy/aluminum foamor a multi-layer composite mold. The surface finish of the compressionwall 54 does not generally need to be of the same quality as that of thecontact wall 40 of the base mold 32 since most of the times, thecompression wall 54 is not directly touching the strengthener, butusually indirectly in communication with the strengthener via themembrane 36.

In operation, the mold assembly 30 is used to manufacture a compositepart by injecting the matrix throughout the strengthener 66. For claritypurposes, the manufacturing process will now be described with referenceto a composite plate formed with the following steps: laying of thestrengthener; placement of the membrane; closure of the mold assembly;application of vacuum to the strengthener chamber; injection of thematrix; injection of the controlling fluid; compaction of the compositepart; solidification of the part; and ejection from the mold assembly.

Laying of the Strengthener

As illustrated in FIG. 7, the strengthener 66 is first positioned in thechamber 38 of the base mold 32. This strengthener 66 is generally the“skeleton” of the composite material, as opposed to the matrix providedby injection to impregnate and fill the strengthener 66. Underatmospheric pressure Pa, the free thickness of the generallynon-compacted strengthener 66 is denoted as h.sub.o.

Placement of the Membrane

As shown in FIG. 8, the membrane 36 is positioned on the base mold 32 inorder to cover the strengthener 66 and over the grooves 48. As statedhereinabove, the base mold 32 and the membrane 36 generally delimit thestrengthener chamber 38 adapted to receive the strengthener 66.

Closure of the Mold Assembly

From FIG. 9, the cover mold 34 is fitted to the base mold 32 via theridges 62 and grooves 48 assembly in order to seal the strengthenerchamber 38 and the compression chamber 52 with the strengthener 66located in the strengthener chamber 38.

Application of Vacuum to the Strengthener Chamber

Optionally, pressure in the strengthener chamber 38 is changed tofacilitate the manufacture of the composite material. As seen in FIG.10, the pressure in the strengthener chamber 38 is set at a vacuumpressure P.sub.v, which is generally lower than atmospheric pressureP.sub.a. To change the pressure in the chamber 38, a vacuum source suchas for example a vacuum pump is generally used through a connection tothe evacuation outlet 44 in the base mold 32 (see arrow 45).

In this case, the resulting pressure applied to the strengthener 66,that is, the ambient atmospheric pressure P.sub.a minus the vacuumpressure P.sub.v, generally compresses the strengthener 66 to athickness h.sub.1 which is less than h.sub.o.

Injection of the Liquid

In FIG. 11, a predetermined quantity of matrix 70 is injected in thechamber 38 via the injection inlet 46 (see arrow 71). At first, aportion of the matrix 70 generally impregnates a fraction of thestrengthener's total volume 72 near where it is injected, and moves inthe strengthener 66 with a matrix flow front 76. The matrix flow front76 gradually moves along a propagation direction generally defined fromthe injection inlet 46 to the evacuation outlet 44.

After injection, a portion of the matrix 70 impregnates a fraction ofthe strengthener's total volume 72 and another portion of the matrixcalled free matrix generates a deformation zone 74 by swelling themembrane 36 which deforms and occupies a portion of the compressionchamber 52. The free matrix is generally the injected matrix 70 whichhas permeated across the strengthener or when the matrix infiltrates onthe sides of the strengthener, generally between the strengthener 66 andthe strengthener chamber 38.

Alternatively, the free matrix swells the membrane 36 to significantlyfill the compression chamber 52. Also alternatively, the deformationzone 74 is generated by the varying thickness of the strengthener 66saturated by the matrix and which, as a result, deforms the membrane 36.

Due to the injection of the matrix 70, the thickness h.sub.1 of thestrengthener chamber 38 generally increases, up to the maximal value hcorresponding to the height of the gap 64.

Once the predetermined quantity of matrix 70 has been injected into thestrengthener chamber 38, the matrix injection inlet 46 is closed, thefluid control aperture 58 is generally obstructed by the swollen portionof the membrane 36, while the vent 60 allows evacuation of the aircontained in the compression chamber 52 (see arrow 61).

Injection of the Controlling Fluid

The controlling fluid may be either a gas or more generally anincompressible liquid such as water, oil or any other liquid meetingspecified requirements. As seen in FIG. 12 the fluid 78 is injected inthe compression chamber 52, through the control aperture 58 (see arrow59), at a temperature T.sub.f and a pressure P.sub.f.

The pressure applied by the controlling fluid 78 on the membrane 36progressively reduces the deformation of the membrane 36, compacts thestrengthener 66 and forces both the matrix which is already in theimpregnated strengthener volume 72 and the free matrix in thedeformation zone 74 along its longitudinal extension.

This step has the effect of bringing the penetration of the matrixtoward the un-impregnated strengthener volume 80 and enables to controlthe progression of the matrix flow front 76 through the strengthener 66along the propagation direction.

By heating the controlling fluid 78 and/or the base mold 32, thetemperature inside the strengthener chamber 38 is regulated. Usually,higher temperatures generally decrease the viscosity of the matrix 70and facilitate its penetration into the strengthener 66. Increasing thecontrolling fluid temperature T.sub.f also generally facilitates theprogression of the matrix flow front 76 through the strengthener 66.

Compaction of the Composite Part

As seen in FIG. 13, when the compression chamber 52 is filled by thecontrolling fluid 78, pressure is increased up to a compaction pressureP.sub.c in order to compress the impregnated strengthener 72 via themembrane 36. This step generally completes the impregnation of thestrengthener 66, increases its saturation, brings the strengthener to agiven thickness h and helps to maintain the contact of the impregnatedstrengthener 72 with the base mold 32.

Indeed, since the application of the compaction pressure P.sub.c isisotropic (i.e. in all directions), the impregnated strengthener 72 isgenerally compacted uniformly, regardless of its geometricalparticularities. Furthermore, it is possible to maintain the compactionpressure P.sub.c during the cure and/or solidification phase, as will bediscussed in more details in the next step, to increase the saturationof the injected part and help impart the surface finish of the contactwall 40 to the injected part.

The compaction pressure P.sub.c being generally greater than atmosphericpressure, the final thickness h of the molded part may be controlled andparts with greater fiber contents can be manufactured. It should benoted that the compaction pressure P.sub.c nevertheless remains belowthe level that would cause permanent deformation of the cover mold 34.Accordingly, the cover mold 34 is designed to withstand the compactionpressure P.sub.c.

Cure and/or Solidification of the Part

The base mold 32 is brought to the desired temperature for the cureand/or solidification of the part 82 by means of thermal resistors 84,schematically illustrated in FIG. 14, or by any other suitable heatingsystem or cooling system (not shown). The thermal resistors 84 are soconfigured as to radiate heat to the base mold 32 to provide means forregulating the temperature of the contact wall 40 of the mold 32.

During this phase, the compaction pressure P.sub.c applied in thecompression chamber 52 helps provide a generally continuous contact ofthe composite part 82 with the contact wall 40 of the base mold 32. Thiscontact has the effect of providing the part 82 with a generallyconformed reproduction of the geometrical and surface finish of thecontact wall 40, and is further optionally used in conjunction with aheating or cooling of the fluid 78, as stated hereinabove.

During the cure and/or solidification of the composite part, the moldhelps to provide a generally continuous contact of the injected part 82with the contact wall 40 which minimizes the surface waviness androughness of the part 82 on its surface adjacent to the contact wall 40.These phenomena sometimes result from polymerization shrinkage in thecase of heat-cured polymers or from matrix contraction during cooling orsolidification of the part 82.

The mold assembly 30 therefore helps to control the cure and/or thesolidification of the injected part 82 such that its generated surfaceappearance is of a generally better quality, since the surface of theinjected part 82 that is adjacent to the base mold 32 optimallyreproduces the finish quality of the contact wall 40. This cure and/orsolidification step also helps to solidify the matrix and to controlmatrix cross-linking and/or micro-structure, which are thephysico-chemical phenomena generally occurring during cure and/orsolidification. In general, cure and/or solidification determines somephysico-chemical properties of the composite part 82 such as for examplemechanical resistance, anti-wear properties and so on.

Depending on the properties desired for the composite part 82 as well asthe means available, the cure method alternatively uses ultra-violet(UV) light. In this case, the base mold 32, the cover mold 34 and themembrane 36 are transparent to this type of radiation.

Ejection from the Mold Assembly

Once the cure and/or solidification are completed, the temperature ofthe base mold 32 is lowered by shutting off the thermal resistorelements 84 and/or by using a cooling system (not shown) so configuredas to decrease the temperature in the strengthener chamber 38.

In the example shown in FIG. 15, ejection of the controlling fluid 78(see arrow 81) by cold air injected at the vent 60 (see arrow 83)contributes at the same time to the cooling of the part 82 before itsremoval from the mold assembly 30. The fluid 78 is therefore evacuatedfrom the compression chamber 52 by pump means (not shown) connected tothe vent 60 and expelled at the fluid control aperture 58. The coolingof the composite part 82 is also alternatively achieved by conduction ofcold through the base mold 32 and the cover mold 34.

Once this fluid evacuation is completed, the mold assembly 30 is openedby removing the cover mold 34 from the base mold 32, as shown in FIG.16. At that stage, the composite part 82 is still enclosed in thestrengthener chamber 38 by the membrane 36 and has a composite thicknessh.sub.2. The membrane 36 is then removed (see arrow 85) from the basemold 32 containing the composite part 82, as shown in FIG. 17

Next, by means of usual methods of de-molding such as for examplecompressed air jets or mechanical ejectors (not shown), the compositepart 82 is extracted from the base mold 32, as illustrated in FIG. 18(see arrow 87). In general, de-molding is facilitated by the use of areleasing agent applied to the contact wall 40 and the peripheral walls42 of the base mold 32 prior to placing the strengthener therein.

According to the present invention, the mold assembly 30 may beoptionally configured by pre-determining the optimal thickness h of thegap 64 defined by the chambers 38, 52. This gap 64 may be determined bymeans of a computer simulation that helps to achieve optimalimpregnation rate conditions throughout the strengthener 66, whilegenerally minimizing the filling time.

Optionally, the total thickness h of the gap 64 does not need to beuniform along the dispersion of the strengthener 66 in the strengthenerchamber 38. Indeed, a variable and adjustable thickness h helps toprovide a more uniform control over the matrix progression in someportions of the strengthener 66 and allows injecting strengtheners ofnon uniform thickness.

For example, the adjustability of thickness h is used in cases where thestrengtheners permeability characteristics need to be regulated orchanged locally during injection, in cases where the final thickness ofthe composite part is not uniform, in cases where divergent orconvergent flow zones exists within the strengthener chamber 38 or incases where inserts (not shown) are included in the gap 64 or mounted onthe base mold 32 and the cover mold 34.

Also optionally, the mold assembly 30 including the base mold 32, thecover mold 34 and the membrane 36 is further provided with a means forachieving dynamic consolidation of the liquid-saturated strengthener asin the VRTM (Vibration Resin Transfer Molding) variation of the RTMprocess for example, or by transmitting the mechanical vibration energydirectly to the fluid.

If dynamic consolidation is used as in the VRTM process during the“compaction of the part” step described hereinabove, the vibration soimposed on the impregnated strengthener 66 contributes to expel theresidual gaseous phase which is sometimes entrapped in the pores of thefibrous strengthener at the end of the compaction phase, before totalsolidification of the matrix.

Also optionally and as introduced in the steps of “Injection of thecontrolling fluid” and “Solidification of the part”, heating and coolingsystems may be included into the mold assembly 30. The heating andcooling systems generally involve one or both molds 32, 34 or thecontrolling fluid 78 during the manufacture of the composite part andmay be achieved by heat transfer such as for example conduction,convection and radiation.

A mold assembly and a method of using the mold assembly according tovarious embodiments of the present invention will now be described withrespect to FIGS. 19 to 32. For concision purposes, only the differencesbetween the mold assemblies and processes of the various followingembodiments and the mold assembly and process illustrated in FIGS. 1 to18 will be described hereinbelow.

A mold assembly 130 and a process of manufacturing a composite partaccording to a second embodiment of the present invention areillustrated in FIG. 19.

In this embodiment, the mold assembly 130 includes a deformable member,show in the illustrative embodiment as a membrane 136 and a deformableelement 131. The deformable element 131 is provided in the compressionchamber 152 and has the effect of generally reducing the volume ofcontrolling fluid injected into the compression chamber 152 via thefluid control aperture 158 and ejected via the vent 160.

The deformable element 131 is generally porous and made from elasticmaterial such as, for example, a foam polymer or any other type of openor closed-pore material. By being machined on its surface facing thestrengthener 166, the deformable element 131 helps impose a shape on thecomposite part being manufactured. The other surface of the deformableelement 131 faces the compression wall 154 of the cover mold 134.

In operation, when injected in the mold assembly 130 by an orifice inthe cover mold (not shown), the deformable element 131 occupies acertain volume of the compression chamber 152 while still facilitating,due to its deformability, the flow of the matrix 170 through thestrengthener 166.

Once the matrix 170 injection is completed, a minimized quantity ofcontrolling fluid 178 is then injected into the compression chamber 152to control the penetration of the matrix 170 into the strengthener 166.The pressure applied to the fluid 178 is transmitted to the strengthener166 through the deformable element 131. In the case of closed-poredeformable elements 131, the fluid control aperture 158 and the vent 160are in communication with the membrane 136 via the deformable element131. Injection of the controlling fluid 178 may generate a film (notshown) in the compression chamber 152, either between the deformableelement 131 and the compression wall 154 or between the membrane 136 andthe deformable element 131.

Alternatively, a series of grooved channels (not shown) are machined onthe surface of the deformable element 131 that is closest to thestrengthener 166 to participate in transmitting pressure to thestrengthener 166. In that case, the membrane 136 deforms in operationand cooperates with the grooves (not shown) of the deformable element131.

It is to be noted that the deformable element 131, instead of beingshaped, is also alternatively injected directly into the cavity createdby the base mold 132 and the cover mold 134 via the fluid controlaperture 158. The mold 132 would nevertheless already have to contain afirst strengthener 166 in order for the injected deformable element 131to take the imprint of the strengthener 166.

In this embodiment generally, if the membrane 136 is removed, theplacement or the injection of the deformable element 131 in thecompression chamber 152 may be used to produce a composite sandwich partwith the deformable element 131 as core. In that case, a strengthener166 is placed next to the deformable element 131 and the controllingfluid 178 is replaced by the matrix 170.

A mold assembly 230 and a process of manufacturing a composite partaccording to a third embodiment of the present invention are illustratedin FIGS. 20 and 21.

In this embodiment, the strengthener 266 is located in the base mold 232and covered with the membrane 236 under which a vacuum may be drawn. Thecover mold 234 includes a compression chamber 252 which allowspressurizing at greater than atmospheric pressure, with the aid ofeither a gas or a liquid.

The cover mold 234 needs not be machined in the compression chamber 252and may include compartmentalized portions (not shown) delimited by thecompression wall 254 which are so configured as to be independentlymovable toward the compression chamber 252 and the strengthener 266.

In operation, the strengthener 266 is first pressurized by compressedgas injected in the compression chamber (see arrow 259), byincompressible fluid or by a combination of incompressible fluid andpressurized tubes, which will further be described hereinbelow. Thecompressed gas generally compresses the strengthener 266 and controlsthe membrane 236 deformation during injection. If the cover mold 234includes compartmentalized portions (not shown), they may be positionedat various levels with respect to the membrane 236 to control thedeformation of the membrane 236 after injection of the matrix in thestrengthener 266 and via the pressure exerted on the compressed gas orcontrol fluid.

With the incompressible fluid, isotropic compression is exerted on thestrengthener 266. Due to the non-compressibility of the fluid 278, localdeformations of the membrane 236 in the saturated zone of thestrengthener 266 generally imply a deformation in the opposite directionand of equivalent volume in the non-saturated zone of the strengthener266.

With the combination of an incompressible fluid 278 and pressurized tube235 extending in the compression chamber 252, as illustrated in FIG. 21,a controllable isotropic pressure is exerted on the strengthener 266 andthe compression chamber 252 by a tube 235 provided into specificlocations above the strengthener 266. The tube 235 is deformable underpressure and includes at least one tube closable on both extremities. Atleast one extremity of the tube 235 is mounted through the cover mold234 for operability while composite parts are being manufactured.

In operation, the pressure of the control fluid 278 is controlled bychanging the pressure in the tube 235. By deforming under pressure whileinjected by a fluid source 278 a, the tube 235 either directlyphysically compresses the membrane 236 and the strengthener 266 orindirectly compresses the membrane 236 and the strengthener 266 via thepressure exerted on the control fluid 278 in the compression chamber252.

It should be noted that in the second embodiment, the temperature in thecompression chamber 252 may also be modified and controlled via thepressurization fluid. With the use of the tubes 235, the heating andcooling of the strengthener 266 may be achieved through theincompressible fluid, while the tubes 235 provide means for evacuatingor dissipating a certain amount of heat or cold from the mold assembly230.

A mold assembly 330 and a process of manufacturing a composite partaccording to a fourth embodiment of the present invention areillustrated in FIGS. 22 to 25.

In this embodiment, the cover mold 334 includes a machined or imprintedchannel network on the compression wall 354 which faces the strengthener366 when the cover mold 334 is mounted on the base mold 332. The networkis so configured as to allow the matrix to spread over an optimizedsurface of the strengthener 366, before using the controlling fluid 378.

The network includes a plurality of passages 339 which are shown in theillustrative embodiment as a generally rectangular grid or a set ofchannels including longitudinal passages 339 a and transversal passages339 b. The distance between the compression wall 354 and the membrane336 is sufficiently small to limit the space in which the matrix flowsabove the strengthener 366.

It is to be noted however that the geometry of the network, includingthe shape and configuration of the passages 339, is generally designedto adapt to the part to manufacture, in order to favor matrixpenetration into specified zones and zones of complex shape of thestrengthener 366 and to minimize the average movement of the matrix fromthe time it is injected in the mold assembly 330 to the moment itimpregnates the strengthener 366. Generally, the passages 339 are ofdimensions such that they can receive a significant portion of theamount of matrix 370 required to wet the strengthener 366 completely.Optionally, the transversal passages 339 b are generally extending inalignment with the diffusion passages 350 and at least one longitudinalpassage 339 a is generally extending in alignment with an injectioninlet 346.

In operation and during injection of the pressurized matrix 370 via theinjection inlet 346 (see arrow 371) and the diffusion passages 350 (onlyone shown), a portion of the strengthener's total volume 372 isimpregnated by the matrix. The free matrix generates the deformationzone 374 and deforms the membrane 336 which mates with the passages 339of the network, expelling the excess of air from the cover mold 334through the vents 360 (see arrow 361), as seen in FIG. 24.

From FIG. 25, it is shown that the injection of the controlling fluid378 via the fluid control aperture 358 (see arrow 359) propagates in thepassages 339 and above the membrane 336 to force the free matrix intothe strengthener 366 and favor a complete impregnation of thestrengthener in the composite part 382.

A mold assembly 430 and a process of manufacturing a composite partaccording to a fifth embodiment of the present invention are illustratedin FIGS. 26 to 28.

In this embodiment, the mold assembly 430 allows the simultaneousmanufacture of several composite parts using a base mold 432 and aplurality of rigid frame assemblies 441 a, 441 b, 441 c, 441 d, 441 e soconfigured as to define a plurality of superimposed double-chamberlayers. Each layer includes a strengthener chamber 438 a, 438 b, 438 c,438 d, 438 e, a respective membrane 436 a, 436 b, 436 c, 436 d, 436 eand a respective compression chamber 452 a, 452 b, 452 c, 452 d, 452 e.

In the illustrative embodiment, each frame assemblies 441 a, 441 b, 441c, 441 d, 441 e includes a separator 443 made of metal or of a more orless rigid foam, defining on one side the contact wall 440 and on theother side the compression wall 454 as described hereinabove. On theside of each compression wall 454, at least one fluid control aperture458 and at least one vent 460 extend through each frame assemblies 441a, 441 b, 441 c, 441 d, 441 e. Also, on the side of each contact wall440, at least one injection inlet 446 and at least one evacuation outlet444 extend through each frame assemblies 441 a, 441 b, 441 c, 441 d, 441e. The base mold 432 and the frame assemblies 441 a, 441 b, 441 c, 441d, 441 e are mounted or stacked one on top of the other as describedhereinabove.

In the illustrative embodiment of FIG. 26, the last frame assembly 441 eincludes a cover reinforcement 434 a which is mounted over its separator443 to provide for additional rigidity and integrity of the moldassembly 430 during the manufacturing of the composite parts.Alternatively, as illustrated in FIGS. 27 and 28, the last frameassembly 441 e is replaced by a cover mold 434 b which has a similarconfiguration as the previously described cover molds.

In operation, each strengthener 466 a, 466 b, 466 c, 466 d, 466 e isplaced in one strengthener chamber 438 a, 438 b, 438 c, 438 d, 438 e andimpregnated with matrix injected via the injection inlets 446 of eachframe assemblies 441 a, 441 b, 441 c, 441 d, 441 e, as illustrated inFIG. 27. The matrix 470 is optionally injected simultaneously into allstrengthener chambers 438 a, 438 b, 438 c, 438 d, 438 e, or with a delaybetween each sequential injection of matrix in the strengtheners.

The controlling fluid 478 is then injected into the compression chambers452 a, 452 b, 452 c, 452 d, 452 e via the fluid control apertures 458(see arrows 459). The excess of fluid contained in the compressionchambers 452 a, 452 b, 452 c, 452 d, 452 e is expelled via the vents 460(see arrows 461). The principle of matrix flow front 476 progression andthe movement of the membranes 436 a, 436 b, 436 c, 436 d, 436 e due tothe free matrix in the deformation zone 474 remains the same, asdescribed in the previous embodiments and for each layer of the moldassembly 430. Injection of the fluid 478 proceeds until the lattercompression chamber 452 e has been completely filled.

As seen in FIG. 28, each composite part 482 e is then compressed betweenthe separator 443 on one side and the membrane 336 e pressurized by thecontrolling fluid 478 on the other side. This step therefore provides agenerally similar degree of compression for all composite parts, whichare at the same time more protected against the risk of defects due towarping, since each face of the strengthener generally sees a similarcompression force.

For the cure and/or the solidification step, the base mold 432 isbrought to the desired temperature as in the general case. Onceinitiated, the polymerization of the liquid matrix is generallyaccompanied by heat dissipation, which participates in upward heat fluxdiffusion, such that this exothermic polymerization reaction occurringin the base mold 432 initiates the cure of the composite part located inthe frame assembly immediately above. The composite parts are thereforesequentially cured in the stack of frame assemblies 441 a, 441 b, 441 c,441 d, 441 e.

The energy used to heat any lower frame assembly is generallytransferred from one layer to the next one rather than being used forcure only a single composite part. It should be noted that heatingelements are optionally included in the vicinity of compression chambers452 a, 452 b, 452 c, 452 d, 452 e or in intermediate combinations offrame assemblies 441 a, 441 b, 441 c, 441 d, 441 e to accelerate thecure process.

A mold assembly 530 and a process of manufacturing a composite partaccording to a sixth embodiment of the present invention are illustratedin FIGS. 29 to 33.

In this embodiment, the mold assembly 530 includes a base mold 532, acover mold 534 and a plurality of frame assemblies 541 a, 541 b, 541 c,541 d. The number of frame assemblies 541 a, 541 b, 541 c, 541 d variesdepending on the number of parts to be manufactured simultaneously.

The mold assembly 530 is also provided with injection inlets 546 andevacuation outlets 544 in order to allow injection of the matrix overthe strengtheners 566 a, 566 b, 566 c, 566 d as well as evacuation ofair and excess matrix. In the illustrative embodiment, the evacuationoutlet 544 and the injection inlet 546 are extending through theplurality of frame assemblies 541 a, 541 b, 541 c, 541 d that arestacked on the base mold 532 and covered by the cover mold 534.

When mounted one on top of the other as described hereinabove, the basemold 532, and the plurality of frame assemblies 541 a, 541 b, 541 c, 541d define a stacking chamber 545 in which layers of strengtheners 566 a,566 b, 566 c, 566 d, separators 543 a, 543 b, 543 c and the cover mold534 are to be alternatively placed one on top of the other.

The separators 543 a, 543 b, 543 c participate in providing the shapeduring the manufacture of the composite parts and include on one side amachined compression wall 554 and on the other side, a machined contactwall 540. The compression wall 554 faces the contact wall 540 of thebase mold 532 or the contact wall 540 of the separator located justbelow.

The separators 543 a, 543 b, 543 c are made from sufficientlycompressible material to allow themselves to generally deform uponinjection of matrix into the strengtheners 566 a, 566 b, 566 c, 566 d,but sufficiently rigid at the same time to transmit the effect of thepressure of the matrix injected into one strengthener to neighboringstrengtheners in the stacking chamber 545.

The cover mold 534 includes a compression wall 554 facing the contactwall 540 of the separator 543 c located below and a punch 547 adapted tocompress via the cover mold 534 the strengtheners 566 a, 566 b, 566 c,566 d and the separators 543 a, 543 b, 543 c contained between the basemold 532 and the cover mold 534. The shapes of the contact walls 540 andthe compression walls 554 are so configured as to define the compositepart to manufacture.

Using this mold assembly 530, several replicates of a same part may beobtained during one manufacturing process, without significantlydiminishing the final composite part quality. This process may also beadapted to the mass production of structural parts, since the surfacefinish obtained by this approach on one side of the composite part isgenerally less critical and does not have to be of the same quality asfor the parts manufactured by the other embodiments describedhereinabove using a compression chamber, a strengthener chamber and amembrane.

In operation, the first strengthener 566 a is slidably placed over thebase mold 532 and laterally held in place by the first frame assembly541 a. The first separator 543 a is then placed above the firststrengthener 566 a. This procedure is repeated the number of timesnecessary to obtain the desired number of composite parts, then thestack of strengtheners 566 a, 566 b, 566 c, 566 d and separators 543 a,543 b 543 c are covered with the cover mold 534.

As seen in the illustrative embodiment of FIG. 30, the method includes asuccessive injection of the matrix 570 into the strengtheners 566 a, 566b, 566 c, 566 d via the injection inlets 546, with a slight delaybetween each injection.

The matrix 570 is injected (see arrows 571) under pressure into thefirst strengthener 566 a, which brings about a deformation of the firstseparator 543 a, as described hereinabove. Since no significant forceopposes the movement of the first separator 543 a, the latter pressesthe second strengthener 566 b along the same direction.

The matrix flow front 576 a progresses along the strengthener 566 a.After the matrix flow front 576 a reaching an optimized progression inthe strengthener 566 a, injection begins in the second strengthener 566b. The matrix 570 injected under pressure produces the same effect asdescribed in the previous paragraph for the first injection, andgenerally deforms the separators located above 543 b and beneath 543 athe second strengthener 566 b. The first strengthener 566 a is thusgenerally compressed over the distance of propagation of the matrix flowfront 576 b into the second strengthener 566 b. All the other injectionsof matrix in subsequent strengtheners are performed in a similar manner.

The last strengthener 566 d has the particularity of not allowing thematrix under pressure injected therethrough to deform the rigid covermold 534 located above the strengthener 566 d. As a result, the matrix570 compresses the layers of strengthener 566 a, 566 b, 566 c locatedunderneath.

The impregnation of the matrix in the strengtheners 566 a, 566 b, 566 c,566 d and the progression of the matrix flow front 576 a, 576 b, 576 c,576 d are thus regulated by the pressure applied by the contact wall 540on the strengtheners 566 a, 566 b, 566 c, 566 d and generallycorresponds to the pressure applied on the strengthener located above.During this impregnation step, the excess of fluid or gas in thevicinity of strengtheners 566 a, 566 b, 566 c, 566 d or the excess ofmatrix may be expelled via the evacuation outlet 544 (see arrows 545).

The compaction step generally increases the fiber content of thecomposite parts manufactured and improves the reproducibility of theparts manufactured in a stack according to this embodiment. This step isusually performed by applying a compression force to the cover mold 534via the punch 547 (see arrow 549), as illustrated in FIG. 31. Thestiffness of the separators 543 a, 543 b, 543 c is generally sufficientto cause compaction of the impregnated strengtheners 582 a, 582 b, 582c, 582 d, in compliance with the geometry of the separators 543 a, 543b, 543 c. For this reason, the crushing of the separators 543 a, 543 b,543 c remains generally minimal.

In this embodiment, the consolidation of the composite parts 582 a, 582b, 582 c, 582 d generally occurs in one direction, which is notnecessarily a direction normal to the surfaces of the composite parts582 a, 582 b, 582 c, 582 d. In the previous embodiments, the compactionof the parts is usually performed by the controlling fluid proving acompression loading normal to the surface of the composite part.

However, a controlling fluid 578 may be optionally injected between thecover mold 534 provided or not with a membrane covering the laststrengthener 582 d. Alternatively, as illustrated in FIG. 33, eachstrengthener 566 a, 566 b, 566 c, 566 d is covered with a membrane 536so configured as to interact with a controlling fluid injectedsimultaneously between each separator 543 a, 543 b, 543 c. In thesecases, the controlling fluid can be injected either into a porousseparator 543 a, 543 b, 543 c, or as illustrated in FIG. 33, directlybetween the separators 543 a, 543 b, 543 c and an added membranecovering the strengtheners 582 a, 582 b, 582 c, 582 d.

Also alternatively, the membrane 536 is inserted between the separators543 a, 543 b, 543 c and the strengtheners 582 a, 582 b, 582 c, 582 d,such that the controlling fluid can still be injected either into theporous separators 543 a, 543 b, 543 c, or directly between theseparators 543 a, 543 b, 543 c and the strengtheners 582 a, 582 b, 582c, 582 d.

The cure step generally corresponds to the cure step described in thefourth embodiment of the present invention. As shown in FIG. 32 of theillustrative embodiment, the compression force is maintained on the moldassembly 530 during the cure and/or the solidification step which moreparticularly involves cure and/or solidification of the first compositepart 582 a followed by the subsequent cure and/or solidification of theremaining composite parts 582 b, 582 c, 582 d (see arrow 551). Once cureis completed, a finishing step is sometimes required to meet finalcomposite part specifications.

A mold assembly 630 and a process of manufacturing a composite partaccording to a seventh embodiment of the present invention areillustrated in FIG. 34.

In this embodiment, the mold assembly 630 includes a porous medium 653provided in the compression chamber 652 of the cover mold 634 whichgenerally controls or reduces the speed at which the fluid injected fromthe fluid control aperture 658 to the vent 660 progresses in thecompression chamber 652. Alternatively, the porous medium is replaced bya granular medium such as for example sand or by a fibrous medium.

The porous medium 653 is a generally deformable element 131 which inoperation, allows the passage of the fluid through itself, but itsporous composition significantly helps to control or restrain thepropagation of the flow of control fluid. In some instances, dependingon the physical properties of the strengthener, of the chemicalproperties of the matrix, of the nature of the control fluid and on thepressure and temperature conditions while the mold assembly 630 is inoperation, the flow propagation of control fluid may need to becontrolled with respect to the flow propagation of the matrix in thestrengthener.

For instance, a control fluid flowing in the compression chamber 652from the fluid control aperture 658 to the vent 660 generally providesan efficient and non-uniform compression of the membrane 636 in theregion swollen by the free matrix so as to facilitate the flow of thefree matrix toward the strengthener. By having a porous medium 653 inthe compression chamber 652, the propagation of the control fluid in thecompression chamber 652 may be delayed such that the control fluid flowfront (not shown) does not go beyond the matrix flow front, in order toefficiently help impregnate the strengthener with the matrix.

Although the present invention has been described hereinabove by way ofembodiments thereof, it can be modified, without departing from thespirit and nature of the subject invention as defined in the appendedclaims.

The invention claimed is:
 1. A method for generating a composite partfrom a strengthener and a matrix comprising: a) sealingly positioning adeformable member in between a first chamber of a first mold portion anda second chamber of a second mold portion, wherein the strengthener islocated within said first chamber and wherein venting fluid is locatedwithin said second chamber; b) injecting the matrix into said firstchamber to at least partially impregnate the strengthener; c)propagating the matrix in and along the strengthener by: (1) injecting acontrolling fluid into said second chamber so as to pressurize a firstportion of said deformable member; and (2) expelling venting fluid fromsaid second chamber; and d) inducing vibrations in the controlling fluidto expel entrapped residual gases from the impregnated strengthener. 2.The method of claim 1, wherein said injecting the matrix into said firstchamber is performed at a vacuum pressure which is lower thanatmospheric pressure.
 3. The method of claim 1, wherein said propagatingthe matrix in and along the strengthener is performed while heating saidcontrolling fluid.
 4. The method of claim 1, further comprising:solidifying the impregnated strengthener to form a composite part at acompaction pressure greater than atmospheric pressure while inducingvibrations in the controlling fluid.
 5. The method of claim 1, furthercomprising: curing the impregnated strengthener with heat transferapplied to at least one of said first and second mold portions.
 6. Themethod of claim 1, wherein said controlling fluid is an incompressiblefluid.
 7. The method of claim 1, further comprising: a matrix injectioninlet for injecting the matrix into said first chamber and a matrixevacuation outlet, said inlet and said outlet defining a propagationdirection.
 8. The method of claim 7, further comprising a fluid aperturefor injecting said controlling fluid into said second chamber, andwherein said fluid aperture for injecting said controlling fluid islocated closer to said matrix injection inlet than to said matrixevacuation outlet.
 9. The method of claim 8, further including a ventfor releasing pressure in said second chamber, the vent being positioneddownstream of said fluid aperture in said propagation direction.
 10. Themethod of claim 7, wherein said matrix injection inlet includes adiffusion passage provided on a contact wall of said first chamber. 11.The method of claim 7, wherein said matrix evacuation outlet isconnectable to a vacuum source to selectively generate at least apartial vacuum in said first chamber.
 12. The method of claim 8, whereinsaid fluid aperture is connectable to a fluid source to generatepressure in said second chamber.
 13. The method of claim 8, wherein saidfluid aperture opens into said second chamber and said matrix injectioninlet opens into said first chamber in a generally similar direction.14. The method of claim 9, wherein said vent is connectable to a vacuumsource to selectively generate at least a partial vacuum in said secondchamber.
 15. The method of claim 9, wherein said vent comprises a valveto regulate the flow of the venting fluid through said vent.
 16. Themethod of claim 1, wherein said deformable membrane is impermeable toliquid.
 17. The method of claim 1, wherein said deformable membrane ispermeable to gas.
 18. The method of claim 1, wherein said second moldportion includes a compression wall and said deformable member isconfigured to contact said compression wall when said controlling fluidis injected into said second chamber.
 19. The method of claim 7,wherein, prior to said injecting the matrix into said first chamber,said second chamber has a substantially uniform thickness along thepropagation direction.
 20. The method of claim 7, wherein, prior to saidinjecting the matrix into said first chamber, said first chamber has anon-uniform thickness along the propagation direction.